1. Field of the Invention
The present invention generally relates to automatic configuration of a computer network, and more specifically to determining an optimal routing to network destinations. A local router is automatically designated for each subnet currently on-line by determining which on-line router is closest to the subnet. Network routers determine distance to each identified subnet (destination) and, after exchanging subnet distance information with neighboring routers, decide whether the next hop to that subnet should be directly to the subnet or to one of its neighboring routers.
2. Description of the Related Art
An overlay network is a “virtual network” that resides on top of another network. This “virtual network” usually needs to be configured, so that the overlay routers know of each other, as well as the destinations within the overlay network. This network configuration process is typically manual. Should an overlay router drop off-line, the overlay network can be incapacitated.
FIG. 1 shows a simplistic exemplary overlay network. A network (solid lines) interconnects a plurality of nodes N. The overlay network (dotted lines) consists of only certain nodes of the network, shown in FIG. 1 as overlay router nodes O1,. Network destinations, e.g., Internet Provider (IP) subnets S, are also shown on the figure. Each subnet would typically have an associated host/server computer (not shown), which is the contact to that subnet from the overlay network.
An overlay network is conventionally configured by a manual process, which has the disadvantage that the network will not be able to respond to changing conditions such as routers dropping off line or coming online or an interruption of an internodal communication link. More specific to the present invention, even having a configured overlay network provided, there needs to be a method of determining an optimal routing to the various subnets S. That is, if a router receives a data packet addressed to a specific subnet Sx, the router must be able to determine how best to forward that data packet.
More specifically, network destinations, meaning the IP subnets S, are conventionally configured to be “local” to particular routers of an overlay network. This configuration is static. While the destination is advertised throughout the network, and many paths may be taken, the last hop for the destination will always be the “locally” configured router. However, this may not be the best last hop for a particular destination. Moreover, the locally configured router may be “down”.